﻿336 The PhiUppine Journal of Science isw 



inary cultivation. The material is placed in a hanging drop, and 

 some suitable nutrient material is added. The drop is inspected 

 and set aside for a preliminary growth. Living organisms may 

 then often be recognized by the chains or groups formed in 

 multiplication. By isolating such a group and selecting an in- 

 dividual from it, one is practically sure of obtaining a viable 

 organism. Spores of fungi may be left until the hypha of 

 germination has begun to form, and then they may be isolated. 

 This preliminary growth need not be continued for more than 

 an hour or two in the case of many bacteria and fungi. One 

 may make a preliminary separation of motile organisms by 

 placing the material containing them at one end of a long hang- 

 ing drop. They may be picked up after they have swarmed to 

 the farther side of the drop. This same device may be used 

 in the partial separation of animals or zoospores of fungi or 

 of algas from bacteria. 



A more motile organism may be partially or wholly separated 

 from a less motile one by this method. By using a peptone solu- 

 tion, cholera vibrios in a drop of fseces may often be separated 

 sufficiently for an agglutination test. 



The separation of spores, cysts, or living animals from bac- 

 teria is usually easy. The larger organism is isolated and placed 

 in a droplet, the smaller the better. The bacteria in the end of 

 the pipette are now discharged on the cover at a convenient 

 distance from the hanging drop, and sterile fluid is added to the 

 isolated organism. If desired, this fluid may be taken from a 

 large hanging drop on the cover. The liquid surrounding the 

 spore or animal is now removed and fresh liquid is supplied, 

 or the organism may be picked out and discharged in a new 

 droplet. This process is repeated until the organism is washed 

 free from bacteria. The process is usualy done most conven- 

 iently under the low power. The organism in a small hanging 

 drop may be inspected with the high power before being trans- 

 ferred. If necessary, a few remaining bacteria may be removed 

 from the spore with a finer pipette, even loosening them from 

 the side of the larger organism. If the bacteria are embedded 

 in some gelatinous material surrounding the spore or animal, 

 it is sometimes impossible to remove them, but I have had no 

 difficulty in wholly freeing amoebse, in cyst or motile condition, 

 from bacteria. The process of washing the spore or animal 

 usually requires only a very few minutes. 



A bacterium may be washed free from any animal exudate in 

 this way. I have obtained successful infections with doses of 

 a single plague bacillus and of a single anthrax bacillus which 



